Microstructure and mechanical properties of concrete with expansive additives are reported compared with ordinary concrete. Samples of long-term concrete (22 years) were collected from an actual building constructed in 1967 with calcium sulfoaluminate (CSA) used as expansive additive. Hydration products were separated from these samples by using heavy media and analyzed by means of DSC, XRD, and FT-IR. The morphology of the mortar portion was observed by SEM. No differences were detected on the carbonation depth and the compressive strength between CSA concrete and ordinary concrete. Qualitative analysis shows that following carbonation of concretes, C-S-H was changed to silica gel or to C-S-H with low Ca/Si ratio and CaCO3, AL(OH)3 gel, and gypsum. Quantitatively, hydration products in carbonated CSA concrete are larger than in carbonated ordinary concrete. Therefore, decomposition rate of AFt by carbonation is slower than that of C-S-H.

There is a need for a new anode for use in the impressed-current cathodic protection (CP) of inland concrete piers, which are deteriorating because of salt-induced corrosion of reinforcing bars. A new water-based conductive coating was used recently on the cathodic protection of some concrete piers in Virginia. Further, as a possible means of eliminating the need for regular site visits to inspect and insure that the CP is functioning properly (which is a disadvantage common to existing CP systems), a microprocessor-based data acquisition device that facilitates remote monitoring was tested with the system. This paper describes the design, installation, and performance of the CP system during its first year of operation.

Determines the relationship between the cracking in loaded reinforced concrete and the corrosion of embedded steel. The test specimens used in this work are 3 m long beams and their constructive dispositions and loadings are in conformity with French specifications (BAEL 83). A salt fog and gas mixture with the same percentage of carbon dioxide and atmospheric air are the two aggressive environments. The authors use the single-replica technique, which enables crack openings of 0.1 micrometer to be discerned by scanning electronic microscope. The loadless initial state of concrete and the load damage state after bending can also be described. At this resolution, the reinforced concrete beams exhibit an absence of microcracks in both initial and loaded states. The study of the diffusion aggressive ions in concrete allows the microstructural state of cement paste-aggregate interfaces to be defined. The authors conclude that damage of the aureole of transition in the tensile zone of bending beams occurs. The aggressive ions quickly reach the reinforcement through the cracking, whatever their widths, and then progress along the embedded tension steel. The influence of concrete cover is clearly proved, as well as the aggressive difference between conservation environments. The authors follow the corrosion development by using steel electrode potential measurements. Previous results are corroborated; in particular, crack existence appears to be an essential parameter but not crack width. The aggressive environment is an important factor that should be taken into consideration by building regulations. Concrete thickness cover is also important, as well as its permeability, but the latter cannot be studied due to the use of only one concrete composition.

The task of providing durable concrete for the construction of industrial structures is complex, not only because the service environment, which is man-made, varies from one industry to another, but quite often because of a combination of a large number of causative, promoting, and accelerating factors. Results of a condition survey conducted on a large number of concrete structures in chemical, fertilizer, and petrochemical industries in India are presented. A multidisciplinary approach to investigating the causes of deterioration involving laboratory and in situ tests, is described, with the help of care studies. Since no specific guidance is available in the relevant codes of practice, a broad classification both in terms of the mechanism and kinetics of deterioration is suggested for such created environments for the design and construction specifications of concrete structures. Methods of protection through structural detailing, workmanship, and materials technology are also outlined.

Polypropylene and steel fiber reinforced concretes have been used by the author in chemical plant environments since 1980. The applications have been primarily for slabs on grade but have also included grade beams, slab overlays, equipment foundations, pedestals, pump pads, containment barriers, and pile caps. This paper compares durability performance of nonfiber reinforced concrete and fiber reinforced concrete in chemical plant locations in Michigan and Kentucky. The primary durability indicator is crack-free, long-wearing concrete. The results of these durability performances are applicable to the concrete industry in general, and specifically to the placement of concrete in chemical plants. The results indicate that the best durability performance was from concrete reinforced with steel fiber, then polypropylene fiber, and finally nonfiber reinforced concrete. The reasons underlying this performance are explored from the perspective of what is needed for scheduling, cost, and performance of concrete in the various projects, and environments to which the concrete is subjected. This investigation was conducted first by the proper design of the concrete mix proportions, and then by follow-up with field surveys, interviews, and calculations.